As a method of performing product surface inspection and the like, there is a generally known method in a related art in which a product is illuminated by using a lighting apparatus which emits light from a bottom surface, and inspection is carried out with reflected light thereof by performing visual check, photographing, or the like in the vicinity of the lighting apparatus.
There is a known lighting apparatus disclosed in Patent Literature 1 as an example of such a lighting apparatus. According to this lighting apparatus, a flexible substrate having an open ring shape is held in a planar state, and then LEDs are implanted all over the flexible substrate with soldering, and the plurality of LEDs is arranged on a recessed surface of a truncated cone by joining or closely holding one cut-off side and the other cut-off side of the flexible substrate such that the LEDs are positioned on the recessed surface side.
Further, there is a known technology disclosed in Patent Literature 2 as another example of the lighting apparatus for performing product surface inspection and the like. According to this lighting apparatus, three or more plate-like circuit boards are integrally connected in a longitudinal direction via foldable flexible members, a composite board is formed by mounting LED elements on at least one surface of the circuit boards, the composite substrate is folded between the circuit boards to form a hollow polygonal cylindrical shape, and an inner surface and/or an outer surface of the polygonal cylindrical body are formed as light emitting surfaces.